Orange Book is the first to give definition to CD-MO and CD-WO. CD-MO is the magneto-optical disc. CD-WO is a write-once recordable compact disc. Now, recordable CD-ROM CD-R, CD-RW with the rapid development, replaced the CD-WO, and developed a DIS13490 new standards. Orange Book also defines the disc, including photos (Photo CD) of the "hybrid" specification.
CD-R (CD Recordable):
It can be written in data or music once, if written, the data can not be changed or deleted, so it has a much higher safety grade to the storage of data.
CD-R has the same file-base as the traditional CD that uses PC materials. CD-R has screw Grooves pressed in the disc instead of pits in the optic rail. During the burning process, the organic dye stuff in the groove will form blisters when exposed to laser, this blister is pit. Once the blister forms, it can not be recovered. So CD-R can be written once.
CD-RW (CD Rewritable):
CD-RW can be read in and erased repeatedly. The repetition can be 1000 times.
CD-RW has the same grooves as the CD-R. They have almost the same theory of recording. But the recording layer is not organic dye stuff but a kind of phase change material. At present, many CD burners can support CD-RW burning. During the erasing process; the phase change material will recover its former status. So CD-RW can be read in many times.